A medical device for traversing an occlusion in a vessel includes a straightening sleeve positioned at a distal aspect of a catheter, a steering sleeve having an arcuate distal end, and a guidewire disposed through the steering sleeve. The steering sleeve has a first position in which the arcuate distal end is straightened within the straightening sleeve, and a second position in which the steering sleeve extends distally past the straightening sleeve to expose the arcuate distal end. The tip of the arcuate distal end of the steering sleeve or the guidewire can be used to pierce the occlusion. An arrangement of hub assemblies with locking mechanisms and motion limiting structures facilitates adjusting and locking the relative positions of the straightening sleeve, the steering sleeve, and the guidewire. Detent mechanisms are associated with the motion limiting structures for providing controlled incremental movement of the sleeves and the guidewire.